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softfloat: Implement fused multiply-add

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Implement fused multiply-add as a softfloat primitive. This implements
"a+b*c" as a single step without any intermediate rounding; it is
specified in IEEE 754-2008 and implemented in a number of CPUs.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Peter Maydell
2011-10-19 16:14:06 +00:00
parent b8b8ea05c4
commit 369be8f618
3 changed files with 619 additions and 0 deletions
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14
fpu/softfloat.h
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@@ -211,6 +211,18 @@ void set_floatx80_rounding_precision(int val STATUS_PARAM);
*----------------------------------------------------------------------------*/
void float_raise( int8 flags STATUS_PARAM);
/*----------------------------------------------------------------------------
| Options to indicate which negations to perform in float*_muladd()
| Using these differs from negating an input or output before calling
| the muladd function in that this means that a NaN doesn't have its
| sign bit inverted before it is propagated.
*----------------------------------------------------------------------------*/
enum {
float_muladd_negate_c = 1,
float_muladd_negate_product = 2,
float_muladd_negate_result = 3,
};
/*----------------------------------------------------------------------------
| Software IEC/IEEE integer-to-floating-point conversion routines.
*----------------------------------------------------------------------------*/
@@ -269,6 +281,7 @@ float32 float32_sub( float32, float32 STATUS_PARAM );
float32 float32_mul( float32, float32 STATUS_PARAM );
float32 float32_div( float32, float32 STATUS_PARAM );
float32 float32_rem( float32, float32 STATUS_PARAM );
float32 float32_muladd(float32, float32, float32, int STATUS_PARAM);
float32 float32_sqrt( float32 STATUS_PARAM );
float32 float32_exp2( float32 STATUS_PARAM );
float32 float32_log2( float32 STATUS_PARAM );
@@ -375,6 +388,7 @@ float64 float64_sub( float64, float64 STATUS_PARAM );
float64 float64_mul( float64, float64 STATUS_PARAM );
float64 float64_div( float64, float64 STATUS_PARAM );
float64 float64_rem( float64, float64 STATUS_PARAM );
float64 float64_muladd(float64, float64, float64, int STATUS_PARAM);
float64 float64_sqrt( float64 STATUS_PARAM );
float64 float64_log2( float64 STATUS_PARAM );
int float64_eq( float64, float64 STATUS_PARAM );